Preheat oven to 350˚F. Line the bottom of a 9-inch springform pan with parchment paper. Spray the pan with baking spray and rub with a paper towel to evenly coat.

In a small bowl, combine ½ cup sugar with 1 tablespoon cinnamon.
Combine baking powder, salt and flour. Stir well.
Peel and core apples, cut into quarters and then cut each quarter into thin slices.
In the bowl of an electric mixer, beat butter and sugar until thick and smooth. Add eggs one at the time, beating for 30 seconds after each addition and stopping to scrape down sides of bowl once or twice .
With mixer on low speed, add flour mixture and mix just until combined.
Combine the apples with the cinnamon/sugar mixture. Add half of the apples to the prepared pan. Pour batter over apples and smooth batter to edges of pan. Starting in the center, add remaining apples in a circular pattern on top of the batter. Sprinkle any remaining cinnamon/sugar mixture over the top of the apples.
Bake cake for one hour. Cover loosely with foil and bake another 15-25 minutes or until set in the center. Check to see if a toothpick inserted in the center comes out clean.
Cool on a baking rack. Serve warm or at room temperature .